1
|
Fenton NM, Qian L, Paine EG, Sharpe LJ, Brown AJ. A paREDOX in the control of cholesterol biosynthesis: Does the NADPH sensor and E3 ubiquitin ligase MARCHF6 protect mammalian cells during oxidative stress by controlling sterol biosynthesis? Bioessays 2024; 46:e2400073. [PMID: 38760877 DOI: 10.1002/bies.202400073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2024] [Revised: 04/30/2024] [Accepted: 05/03/2024] [Indexed: 05/19/2024]
Abstract
Sterols and the reductant nicotinamide adenine dinucleotide phosphate (NADPH), essential for eukaryotic life, arose because of, and as an adaptation to, rising levels of molecular oxygen (O2). Hence, the NADPH and O2-intensive process of sterol biosynthesis is inextricably linked to redox status. In mammals, cholesterol biosynthesis is exquisitely regulated post-translationally by multiple E3 ubiquitin ligases, with membrane associated Really Interesting New Gene (RING) C3HC4 finger 6 (MARCHF6) degrading at least six enzymes in the pathway. Intriguingly, all these MARCHF6-dependent enzymes require NADPH. Moreover, MARCHF6 is activated by NADPH, although what this means for control of cholesterol synthesis is unclear. Indeed, this presents a paradox for how NADPH regulates this vital pathway, since NADPH is a cofactor in cholesterol biosynthesis and yet, low levels of NADPH should spare cholesterol biosynthesis enzymes targeted by MARCHF6 by reducing its activity. We speculate MARCHF6 helps mammalian cells adapt to oxidative stress (signified by low NADPH levels) by reducing degradation of cholesterogenic enzymes, thereby maintaining synthesis of protective cholesterol.
Collapse
Affiliation(s)
- Nicole M Fenton
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Lydia Qian
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Eloise G Paine
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Laura J Sharpe
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia
| |
Collapse
|
2
|
Loix M, Zelcer N, Bogie JFJ, Hendriks JJA. The ubiquitous role of ubiquitination in lipid metabolism. Trends Cell Biol 2024; 34:416-429. [PMID: 37770289 DOI: 10.1016/j.tcb.2023.09.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 08/17/2023] [Accepted: 09/01/2023] [Indexed: 09/30/2023]
Abstract
Lipids are essential molecules that play key roles in cell physiology by serving as structural components, for storage of energy, and in signal transduction. Hence, efficient regulation and maintenance of lipid homeostasis are crucial for normal cellular and tissue function. In the past decade, increasing research has shown the importance of ubiquitination in regulating the stability of key players in different aspects of lipid metabolism. This review describes recent insights into the regulation of lipid metabolism by ubiquitin signaling, discusses how ubiquitination can be targeted in diseases characterized by lipid dysregulation, and identifies areas that require further research.
Collapse
Affiliation(s)
- Melanie Loix
- Biomedical Research Institute, School of Life Sciences, Hasselt University, Diepenbeek, Belgium; University MS Center Hasselt, Pelt, Belgium
| | - Noam Zelcer
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Amsterdam, The Netherlands
| | - Jeroen F J Bogie
- Biomedical Research Institute, School of Life Sciences, Hasselt University, Diepenbeek, Belgium; University MS Center Hasselt, Pelt, Belgium
| | - Jerome J A Hendriks
- Biomedical Research Institute, School of Life Sciences, Hasselt University, Diepenbeek, Belgium; University MS Center Hasselt, Pelt, Belgium.
| |
Collapse
|
3
|
Zhang L, Cao Z, Hong Y, He H, Chen L, Yu Z, Gao Y. Squalene Epoxidase: Its Regulations and Links with Cancers. Int J Mol Sci 2024; 25:3874. [PMID: 38612682 PMCID: PMC11011400 DOI: 10.3390/ijms25073874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Revised: 03/09/2024] [Accepted: 03/19/2024] [Indexed: 04/14/2024] Open
Abstract
Squalene epoxidase (SQLE) is a key enzyme in the mevalonate-cholesterol pathway that plays a critical role in cellular physiological processes. It converts squalene to 2,3-epoxysqualene and catalyzes the first oxygenation step in the pathway. Recently, intensive efforts have been made to extend the current knowledge of SQLE in cancers through functional and mechanistic studies. However, the underlying mechanisms and the role of SQLE in cancers have not been fully elucidated yet. In this review, we retrospected current knowledge of SQLE as a rate-limiting enzyme in the mevalonate-cholesterol pathway, while shedding light on its potential as a diagnostic and prognostic marker, and revealed its therapeutic values in cancers. We showed that SQLE is regulated at different levels and is involved in the crosstalk with iron-dependent cell death. Particularly, we systemically reviewed the research findings on the role of SQLE in different cancers. Finally, we discussed the therapeutic implications of SQLE inhibitors and summarized their potential clinical values. Overall, this review discussed the multifaceted mechanisms that involve SQLE to present a vivid panorama of SQLE in cancers.
Collapse
Affiliation(s)
- Lin Zhang
- Department of Thoracic Surgery, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital & Shenzhen Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shenzhen 518116, China
| | - Zheng Cao
- Department of Pathology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China
| | - Yuheng Hong
- Department of Thoracic Surgery, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China
| | - Haihua He
- Department of Thoracic Surgery, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China
- Department of Oncology, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Leifeng Chen
- Department of Thoracic Surgery, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China
- Department of Oncology, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Zhentao Yu
- Department of Thoracic Surgery, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital & Shenzhen Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shenzhen 518116, China
| | - Yibo Gao
- Central Laboratory & Shenzhen Key Laboratory of Epigenetics and Precision Medicine for Cancers, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital & Shenzhen Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shenzhen 518116, China
- State Key Laboratory of Molecular Oncology, National Cancer Center, National Clinical Research Center for Cancer, Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China
- Laboratory of Translational Medicine, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China
| |
Collapse
|
4
|
Botsch JJ, Junker R, Sorgenfrei M, Ogger PP, Stier L, von Gronau S, Murray PJ, Seeger MA, Schulman BA, Bräuning B. Doa10/MARCH6 architecture interconnects E3 ligase activity with lipid-binding transmembrane channel to regulate SQLE. Nat Commun 2024; 15:410. [PMID: 38195637 PMCID: PMC10776854 DOI: 10.1038/s41467-023-44670-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 12/19/2023] [Indexed: 01/11/2024] Open
Abstract
Transmembrane E3 ligases play crucial roles in homeostasis. Much protein and organelle quality control, and metabolic regulation, are determined by ER-resident MARCH6 E3 ligases, including Doa10 in yeast. Here, we present Doa10/MARCH6 structural analysis by cryo-EM and AlphaFold predictions, and a structure-based mutagenesis campaign. The majority of Doa10/MARCH6 adopts a unique circular structure within the membrane. This channel is established by a lipid-binding scaffold, and gated by a flexible helical bundle. The ubiquitylation active site is positioned over the channel by connections between the cytosolic E3 ligase RING domain and the membrane-spanning scaffold and gate. Here, by assaying 95 MARCH6 variants for effects on stability of the well-characterized substrate SQLE, which regulates cholesterol levels, we reveal crucial roles of the gated channel and RING domain consistent with AlphaFold-models of substrate-engaged and ubiquitylation complexes. SQLE degradation further depends on connections between the channel and RING domain, and lipid binding sites, revealing how interconnected Doa10/MARCH6 elements could orchestrate metabolic signals, substrate binding, and E3 ligase activity.
Collapse
Affiliation(s)
- J Josephine Botsch
- Department of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152, Martinsried, Germany
- Technical University of Munich, School of Natural Sciences, Munich, Germany
| | - Roswitha Junker
- Department of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152, Martinsried, Germany
| | - Michèle Sorgenfrei
- Institute of Medical Microbiology, University of Zurich, Gloriastrasse 28/30, 8006, Zurich, Switzerland
| | - Patricia P Ogger
- Research Group of Immunoregulation, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152, Martinsried, Germany
| | - Luca Stier
- Department of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152, Martinsried, Germany
- Technical University of Munich, School of Natural Sciences, Munich, Germany
| | - Susanne von Gronau
- Department of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152, Martinsried, Germany
| | - Peter J Murray
- Research Group of Immunoregulation, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152, Martinsried, Germany
| | - Markus A Seeger
- Institute of Medical Microbiology, University of Zurich, Gloriastrasse 28/30, 8006, Zurich, Switzerland
| | - Brenda A Schulman
- Department of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152, Martinsried, Germany.
| | - Bastian Bräuning
- Department of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152, Martinsried, Germany.
| |
Collapse
|
5
|
Gawden-Bone CM, Lehner PJ, Volkmar N. As a matter of fat: Emerging roles of lipid-sensitive E3 ubiquitin ligases. Bioessays 2023; 45:e2300139. [PMID: 37890275 DOI: 10.1002/bies.202300139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 09/22/2023] [Accepted: 09/26/2023] [Indexed: 10/29/2023]
Abstract
The dynamic structure and composition of lipid membranes need to be tightly regulated to control the vast array of cellular processes from cell and organelle morphology to protein-protein interactions and signal transduction pathways. To maintain membrane integrity, sense-and-response systems monitor and adjust membrane lipid composition to the ever-changing cellular environment, but only a relatively small number of control systems have been described. Here, we explore the emerging role of the ubiquitin-proteasome system in monitoring and maintaining membrane lipid composition. We focus on the ER-resident RNF145 E3 ubiquitin ligase, its role in regulating adiponectin receptor 2 (ADIPOR2), its lipid hydrolase substrate, and the broader implications for understanding the homeostatic processes that fine-tune cellular membrane composition.
Collapse
Affiliation(s)
- Christian M Gawden-Bone
- Cambridge Institute of Therapeutic Immunology & Infectious Disease (CITIID), Jeffrey Cheah Biomedical Centre, University of Cambridge, Cambridge, UK
| | - Paul J Lehner
- Cambridge Institute of Therapeutic Immunology & Infectious Disease (CITIID), Jeffrey Cheah Biomedical Centre, University of Cambridge, Cambridge, UK
| | - Norbert Volkmar
- Institute for Molecular Systems Biology (IMSB), ETH Zürich, Zürich, Switzerland
| |
Collapse
|
6
|
Yang J, Lee Y, Hwang CS. The ubiquitin-proteasome system links NADPH metabolism to ferroptosis. Trends Cell Biol 2023; 33:1088-1103. [PMID: 37558595 DOI: 10.1016/j.tcb.2023.07.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 07/07/2023] [Accepted: 07/11/2023] [Indexed: 08/11/2023]
Abstract
Ferroptosis is the type of cell death arising from uncontrolled and excessive lipid peroxidation. NADPH is essential for ferroptosis regulation because it supplies reducing equivalents for antioxidant defense systems and contributes to the generation of reactive oxygen species. Moreover, NADPH level serves as a biomarker for predicting the sensitivity of cells to ferroptosis. The ubiquitin-proteasome system governs the stability of many ferroptosis effectors. Recent research has revealed MARCHF6, the endoplasmic reticulum ubiquitin ligase, as an unprecedented NADPH sensor in the ubiquitin system and a critical regulator of ferroptosis involved in tumorigenesis and fetal development. This review summarizes the current understanding of NADPH metabolism and the ubiquitin-proteasome system in regulating ferroptosis and highlights the emerging importance of MARCHF6 as a vital connector between NADPH metabolism and ferroptosis.
Collapse
Affiliation(s)
- Jihye Yang
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Republic of Korea
| | - Yoontae Lee
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Republic of Korea
| | - Cheol-Sang Hwang
- Department of Life Sciences, Korea University, Seoul, Republic of Korea.
| |
Collapse
|
7
|
Christianson JC, Jarosch E, Sommer T. Mechanisms of substrate processing during ER-associated protein degradation. Nat Rev Mol Cell Biol 2023; 24:777-796. [PMID: 37528230 DOI: 10.1038/s41580-023-00633-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/20/2023] [Indexed: 08/03/2023]
Abstract
Maintaining proteome integrity is essential for long-term viability of all organisms and is overseen by intrinsic quality control mechanisms. The secretory pathway of eukaryotes poses a challenge for such quality assurance as proteins destined for secretion enter the endoplasmic reticulum (ER) and become spatially segregated from the cytosolic machinery responsible for disposal of aberrant (misfolded or otherwise damaged) or superfluous polypeptides. The elegant solution provided by evolution is ER-membrane-bound ubiquitylation machinery that recognizes misfolded or surplus proteins or by-products of protein biosynthesis in the ER and delivers them to 26S proteasomes for degradation. ER-associated protein degradation (ERAD) collectively describes this specialized arm of protein quality control via the ubiquitin-proteasome system. But, instead of providing a single strategy to remove defective or unwanted proteins, ERAD represents a collection of independent processes that exhibit distinct yet overlapping selectivity for a wide range of substrates. Not surprisingly, ER-membrane-embedded ubiquitin ligases (ER-E3s) act as central hubs for each of these separate ERAD disposal routes. In these processes, ER-E3s cooperate with a plethora of specialized factors, coordinating recognition, transport and ubiquitylation of undesirable secretory, membrane and cytoplasmic proteins. In this Review, we focus on substrate processing during ERAD, highlighting common threads as well as differences between the many routes via ERAD.
Collapse
Affiliation(s)
- John C Christianson
- Botnar Research Centre, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK.
| | - Ernst Jarosch
- Max-Delbrück-Centrer for Molecular Medicine in Helmholtz Association, Berlin-Buch, Germany
| | - Thomas Sommer
- Max-Delbrück-Centrer for Molecular Medicine in Helmholtz Association, Berlin-Buch, Germany.
- Institute for Biology, Humboldt Universität zu Berlin, Berlin, Germany.
| |
Collapse
|
8
|
Jeong Y, Oh AR, Jung YH, Gi H, Kim YU, Kim K. Targeting E3 ubiquitin ligases and their adaptors as a therapeutic strategy for metabolic diseases. Exp Mol Med 2023; 55:2097-2104. [PMID: 37779139 PMCID: PMC10618535 DOI: 10.1038/s12276-023-01087-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 06/23/2023] [Accepted: 07/06/2023] [Indexed: 10/03/2023] Open
Abstract
Posttranslational modification of proteins via ubiquitination determines their activation, translocation, dysregulation, or degradation. This process targets a large number of cellular proteins, affecting all biological pathways involved in the cell cycle, development, growth, and differentiation. Thus, aberrant regulation of ubiquitination is likely associated with several diseases, including various types of metabolic diseases. Among the ubiquitin enzymes, E3 ubiquitin ligases are regarded as the most influential ubiquitin enzymes due to their ability to selectively bind and recruit target substrates for ubiquitination. Continued research on the regulatory mechanisms of E3 ligases and their adaptors in metabolic diseases will further stimulate the discovery of new targets and accelerate the development of therapeutic options for metabolic diseases. In this review, based on recent discoveries, we summarize new insights into the roles of E3 ubiquitin ligases and their adaptors in the pathogenesis of metabolic diseases by highlighting recent evidence obtained in both human and animal model studies.
Collapse
Affiliation(s)
- Yelin Jeong
- Department of Biomedical Sciences, College of Medicine, Inha University, Incheon, Republic of Korea
- Program in Biomedical Science & Engineering, Inha University, Incheon, Republic of Korea
- Research Center for Controlling Intercellular Communication (RCIC), College of Medicine, Inha University, Incheon, 22212, Republic of Korea
| | - Ah-Reum Oh
- Department of Biomedical Sciences, College of Medicine, Inha University, Incheon, Republic of Korea
- Program in Biomedical Science & Engineering, Inha University, Incheon, Republic of Korea
- Research Center for Controlling Intercellular Communication (RCIC), College of Medicine, Inha University, Incheon, 22212, Republic of Korea
| | - Young Hoon Jung
- Department of Biomedical Sciences, College of Medicine, Inha University, Incheon, Republic of Korea
- Program in Biomedical Science & Engineering, Inha University, Incheon, Republic of Korea
- Research Center for Controlling Intercellular Communication (RCIC), College of Medicine, Inha University, Incheon, 22212, Republic of Korea
| | - HyunJoon Gi
- Department of Biomedical Sciences, College of Medicine, Inha University, Incheon, Republic of Korea
- Program in Biomedical Science & Engineering, Inha University, Incheon, Republic of Korea
- Research Center for Controlling Intercellular Communication (RCIC), College of Medicine, Inha University, Incheon, 22212, Republic of Korea
| | - Young Un Kim
- Department of Biomedical Sciences, College of Medicine, Inha University, Incheon, Republic of Korea
- Program in Biomedical Science & Engineering, Inha University, Incheon, Republic of Korea
- Research Center for Controlling Intercellular Communication (RCIC), College of Medicine, Inha University, Incheon, 22212, Republic of Korea
| | - KyeongJin Kim
- Department of Biomedical Sciences, College of Medicine, Inha University, Incheon, Republic of Korea.
- Program in Biomedical Science & Engineering, Inha University, Incheon, Republic of Korea.
- Research Center for Controlling Intercellular Communication (RCIC), College of Medicine, Inha University, Incheon, 22212, Republic of Korea.
| |
Collapse
|
9
|
Kambarev S, Borghesan E, Miller CN, Myeni S, Celli J. The Brucella abortus Type IV Effector BspA Inhibits MARCH6-Dependent ERAD To Promote Intracellular Growth. Infect Immun 2023; 91:e0013023. [PMID: 37129527 PMCID: PMC10187129 DOI: 10.1128/iai.00130-23] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 04/10/2023] [Indexed: 05/03/2023] Open
Abstract
Brucella abortus, the intracellular causative agent of brucellosis, relies on type IV secretion system (T4SS) effector-mediated modulation of host cell functions to establish a replicative niche, the Brucella-containing vacuole (BCV). Brucella exploits the host's endocytic, secretory, and autophagic pathways to modulate the nature and function of its vacuole from an endocytic BCV (eBCV) to an endoplasmic reticulum (ER)-derived replicative BCV (rBCV) to an autophagic egress BCV (aBCV). A role for the host ER-associated degradation pathway (ERAD) in the B. abortus intracellular cycle was recently uncovered, as it is enhanced by the T4SS effector BspL to control the timing of aBCV-mediated egress. Here, we show that the T4SS effector BspA also interferes with ERAD, yet to promote B. abortus intracellular proliferation. BspA was required for B. abortus replication in bone marrow-derived macrophages and interacts with membrane-associated RING-CH-type finger 6 (MARCH6), a host E3 ubiquitin ligase involved in ERAD. Pharmacological inhibition of ERAD and small interfering RNA (siRNA) depletion of MARCH6 did not affect the replication of wild-type B. abortus but rescued the replication defect of a bspA deletion mutant, while depletion of the ERAD component UbxD8 affected replication of B. abortus and rescued the replication defect of the bspA mutant. BspA affected the degradation of ERAD substrates and destabilized the MARCH6 E3 ligase complex. Taken together, these findings indicate that BspA inhibits the host ERAD pathway via targeting of MARCH6 to promote B. abortus intracellular growth. Our data reveal that targeting ERAD components by type IV effectors emerges as a multifaceted theme in Brucella pathogenesis.
Collapse
Affiliation(s)
- Stanimir Kambarev
- Paul G. Allen School for Global Health, Washington State University, Pullman, Washington, USA
| | - Elizabeth Borghesan
- Paul G. Allen School for Global Health, Washington State University, Pullman, Washington, USA
| | - Cheryl N. Miller
- Paul G. Allen School for Global Health, Washington State University, Pullman, Washington, USA
| | - Sebenzile Myeni
- Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Jean Celli
- Paul G. Allen School for Global Health, Washington State University, Pullman, Washington, USA
- Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
- Department of Microbiology and Molecular Genetics, Larner College of Medicine at the University of Vermont, Burlington, Vermont, USA
| |
Collapse
|
10
|
Qian L, Scott NA, Capell-Hattam IM, Draper EA, Fenton NM, Luu W, Sharpe LJ, Brown AJ. Cholesterol synthesis enzyme SC4MOL is fine-tuned by sterols and targeted for degradation by the E3 ligase MARCHF6. J Lipid Res 2023; 64:100362. [PMID: 36958722 PMCID: PMC10176258 DOI: 10.1016/j.jlr.2023.100362] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 02/09/2023] [Accepted: 02/25/2023] [Indexed: 03/25/2023] Open
Abstract
Cholesterol biosynthesis is a highly regulated pathway, with over 20 enzymes controlled at the transcriptional and post-translational level. Whilst some enzymes remain stable, increased sterol levels can trigger degradation of several synthesis enzymes via the ubiquitin-proteasome system. Of note, we previously identified four cholesterol synthesis enzymes as substrates for one E3 ubiquitin ligase, membrane-associated RING-CH-type finger 6 (MARCHF6). Whether MARCHF6 targets the cholesterol synthesis pathway at other points is unknown. In addition, the post-translational regulation of many cholesterol synthesis enzymes, including the C4-demethylation complex (sterol-C4-methyl oxidase-like, SC4MOL; NAD(P) dependent steroid dehydrogenase-like, NSDHL; hydroxysteroid 17-beta dehydrogenase, HSD17B7) is largely uncharacterized. Using cultured mammalian cell-lines (human-derived and Chinese Hamster Ovary cells), we show SC4MOL, the first acting enzyme of C4-demethylation, is a MARCHF6 substrate, and is rapidly turned over and sensitive to sterols. Sterol depletion stabilizes SC4MOL protein levels, whilst sterol excess downregulates both transcript and protein levels. Furthermore, we found SC4MOL depletion by siRNA results in a significant decrease in total cell cholesterol. Thus, our work indicates SC4MOL is the most regulated enzyme in the C4-demethylation complex. Our results further implicate MARCHF6 as a crucial post-translational regulator of cholesterol synthesis, with this E3 ubiquitin ligase controlling levels of at least five enzymes of the pathway.
Collapse
Affiliation(s)
- Lydia Qian
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Nicola A Scott
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Isabelle M Capell-Hattam
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Eliza A Draper
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Nicole M Fenton
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Winnie Luu
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Laura J Sharpe
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia.
| |
Collapse
|
11
|
Kennelly JP, Tontonoz P. Cholesterol Transport to the Endoplasmic Reticulum. Cold Spring Harb Perspect Biol 2023; 15:cshperspect.a041263. [PMID: 35940908 PMCID: PMC9899650 DOI: 10.1101/cshperspect.a041263] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Most cholesterol in mammalian cells is stored in the plasma membrane (PM). Cholesterol transport from the PM to low-sterol regulatory regions of the endoplasmic reticulum (ER) controls cholesterol synthesis and uptake, and thereby influences the rates of cholesterol flux between tissues of complex organisms. Cholesterol transfer to the ER is also required for steroidogenesis, oxysterol and bile acid synthesis, and cholesterol esterification. The ER-resident Aster proteins (Aster-A, -B, and -C) form contacts with the PM to move cholesterol to the ER in mammals. Mice lacking Aster-B have low adrenal cholesteryl ester stores and impaired steroidogenesis because of a defect in cholesterol transport from high-density lipoprotein (HDL) to the ER. This work reviews the molecular characteristics of Asters, their role in HDL- and low-density lipoprotein (LDL)-cholesterol movement, and how cholesterol transferred to the ER is utilized by cells. The roles of other lipid transporters and of membrane lipid organization in maintaining aspects of cholesterol homeostasis are also highlighted.
Collapse
Affiliation(s)
- John P Kennelly
- Department of Pathology and Laboratory Medicine, Department of Biological Chemistry, Molecular Biology Institute, University of California, Los Angeles, California 90095, USA
| | - Peter Tontonoz
- Department of Pathology and Laboratory Medicine, Department of Biological Chemistry, Molecular Biology Institute, University of California, Los Angeles, California 90095, USA
| |
Collapse
|
12
|
Coates HW, Capell-Hattam IM, Olzomer EM, Du X, Farrell R, Yang H, Byrne FL, Brown AJ. Hypoxia truncates and constitutively activates the key cholesterol synthesis enzyme squalene monooxygenase. eLife 2023; 12:82843. [PMID: 36655986 PMCID: PMC9851614 DOI: 10.7554/elife.82843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 12/13/2022] [Indexed: 01/20/2023] Open
Abstract
Cholesterol synthesis is both energy- and oxygen-intensive, yet relatively little is known of the regulatory effects of hypoxia on pathway enzymes. We previously showed that the rate-limiting and first oxygen-dependent enzyme of the committed cholesterol synthesis pathway, squalene monooxygenase (SM), can undergo partial proteasomal degradation that renders it constitutively active. Here, we show hypoxia is a physiological trigger for this truncation, which occurs through a two-part mechanism: (1) increased targeting of SM to the proteasome via stabilization of the E3 ubiquitin ligase MARCHF6 and (2) accumulation of the SM substrate, squalene, which impedes the complete degradation of SM and liberates its truncated form. This preserves SM activity and downstream pathway flux during hypoxia. These results uncover a feedforward mechanism that allows SM to accommodate fluctuating substrate levels and may contribute to its widely reported oncogenic properties.
Collapse
Affiliation(s)
- Hudson W Coates
- School of Biotechnology and Biomolecular Sciences, UNSW SydneySydneyAustralia
| | | | - Ellen M Olzomer
- School of Biotechnology and Biomolecular Sciences, UNSW SydneySydneyAustralia
| | - Ximing Du
- School of Biotechnology and Biomolecular Sciences, UNSW SydneySydneyAustralia
| | - Rhonda Farrell
- Prince of Wales Private HospitalRandwickAustralia
- Chris O’Brien LifehouseCamperdownAustralia
| | - Hongyuan Yang
- School of Biotechnology and Biomolecular Sciences, UNSW SydneySydneyAustralia
| | - Frances L Byrne
- School of Biotechnology and Biomolecular Sciences, UNSW SydneySydneyAustralia
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Sciences, UNSW SydneySydneyAustralia
| |
Collapse
|
13
|
Controlling an E3 ligase and its substrate: A function for MARCHF6 circRNA. Biochim Biophys Acta Mol Cell Biol Lipids 2023; 1868:159237. [PMID: 36183995 DOI: 10.1016/j.bbalip.2022.159237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 09/20/2022] [Accepted: 09/22/2022] [Indexed: 11/22/2022]
|
14
|
Zou Y, Zhang H, Bi F, Tang Q, Xu H. Targeting the key cholesterol biosynthesis enzyme squalene monooxygenasefor cancer therapy. Front Oncol 2022; 12:938502. [PMID: 36091156 PMCID: PMC9449579 DOI: 10.3389/fonc.2022.938502] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 07/26/2022] [Indexed: 11/22/2022] Open
Abstract
Cholesterol metabolism is often dysregulated in cancer. Squalene monooxygenase (SQLE) is the second rate-limiting enzyme involved in cholesterol synthesis. Since the discovery of SQLE dysregulation in cancer, compelling evidence has indicated that SQLE plays a vital role in cancer initiation and progression and is a promising therapeutic target for cancer treatment. In this review, we provide an overview of the role and regulation of SQLE in cancer and summarize the updates of antitumor therapy targeting SQLE.
Collapse
Affiliation(s)
- Yuheng Zou
- Department of Medical Oncology, Cancer Center and Laboratory of Molecular Targeted Therapy in Oncology, West China Hospital, Sichuan University, Chengdu, China
| | - Hongying Zhang
- Laboratory of Oncogene, West China Hospital, Sichuan University, Chengdu, China
| | - Feng Bi
- Department of Medical Oncology, Cancer Center and Laboratory of Molecular Targeted Therapy in Oncology, West China Hospital, Sichuan University, Chengdu, China
| | - Qiulin Tang
- Department of Medical Oncology, Cancer Center and Laboratory of Molecular Targeted Therapy in Oncology, West China Hospital, Sichuan University, Chengdu, China
- *Correspondence: Qiulin Tang, ; Huanji Xu,
| | - Huanji Xu
- Department of Medical Oncology, Cancer Center and Laboratory of Molecular Targeted Therapy in Oncology, West China Hospital, Sichuan University, Chengdu, China
- *Correspondence: Qiulin Tang, ; Huanji Xu,
| |
Collapse
|
15
|
Affiliation(s)
- Chao Mao
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Boyi Gan
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
- The University of Texas MD Anderson UTHealth Graduate School of Biomedical Sciences, Houston, TX, USA.
| |
Collapse
|
16
|
Merklinger L, Bauer J, Pedersen PA, Damgaard RB, Morth JP. Phospholipids alter activity and stability of mitochondrial membrane-bound ubiquitin ligase MARCH5. Life Sci Alliance 2022; 5:5/8/e202101309. [PMID: 35459736 PMCID: PMC9034062 DOI: 10.26508/lsa.202101309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2021] [Revised: 04/05/2022] [Accepted: 04/07/2022] [Indexed: 11/24/2022] Open
Abstract
This study shows that lipids can act as regulators for the ubiquitination process and can control the stability and activity of a membrane-embedded E3 ubiquitin ligase. Mitochondrial homeostasis is tightly controlled by ubiquitination. The mitochondrial integral membrane ubiquitin ligase MARCH5 is a crucial regulator of mitochondrial membrane fission, fusion, and disposal through mitophagy. In addition, the lipid composition of mitochondrial membranes can determine mitochondrial dynamics and organelle turnover. However, how lipids influence the ubiquitination processes that control mitochondrial homeostasis remains unknown. Here, we show that lipids common to the mitochondrial membranes interact with MARCH5 and affect its activity and stability depending on the lipid composition in vitro. As the only one of the tested lipids, cardiolipin binding to purified MARCH5 induces a significant decrease in thermal stability, whereas stabilisation increases the strongest in the presence of phosphatidic acid. Furthermore, we observe that the addition of lipids to purified MARCH5 alters the ubiquitination pattern. Specifically, cardiolipin enhances auto-ubiquitination of MARCH5. Our work shows that lipids can directly affect the activity of ubiquitin ligases and suggests that the lipid composition in mitochondrial membranes could control ubiquitination-dependent mechanisms that regulate the dynamics and turnover of mitochondria.
Collapse
Affiliation(s)
- Lisa Merklinger
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Lyngby, Denmark
| | - Johannes Bauer
- Centre for Molecular Medicine Norway (NCMM), Nordic EMBL Partnership University of Oslo, Oslo, Norway
| | - Per A Pedersen
- Department of Biology, University Copenhagen, August Krogh Bygningen, Copenhagen, Denmark
| | - Rune Busk Damgaard
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Lyngby, Denmark
| | - J Preben Morth
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Lyngby, Denmark
| |
Collapse
|
17
|
Christianson JC, Carvalho P. Order through destruction: how ER-associated protein degradation contributes to organelle homeostasis. EMBO J 2022; 41:e109845. [PMID: 35170763 PMCID: PMC8922271 DOI: 10.15252/embj.2021109845] [Citation(s) in RCA: 57] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 01/09/2022] [Accepted: 01/25/2022] [Indexed: 12/24/2022] Open
Abstract
The endoplasmic reticulum (ER) is a large, dynamic, and multifunctional organelle. ER protein homeostasis is essential for the coordination of its diverse functions and depends on ER-associated protein degradation (ERAD). The latter process selects target proteins in the lumen and membrane of the ER, promotes their ubiquitination, and facilitates their delivery into the cytosol for degradation by the proteasome. Originally characterized for a role in the degradation of misfolded proteins and rate-limiting enzymes of sterol biosynthesis, the many branches of ERAD now appear to control the levels of a wider range of substrates and influence more broadly the organization and functions of the ER, as well as its interactions with adjacent organelles. Here, we discuss recent mechanistic advances in our understanding of ERAD and of its consequences for the regulation of ER functions.
Collapse
Affiliation(s)
- John C Christianson
- Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal SciencesBotnar Research CentreUniversity of OxfordOxfordUK
| | - Pedro Carvalho
- Sir William Dunn School of PathologyUniversity of OxfordOxfordUK
| |
Collapse
|
18
|
Wu X, Yan R, Cao P, Qian H, Yan N. Structural advances in sterol-sensing domain-containing proteins. Trends Biochem Sci 2022; 47:289-300. [PMID: 35012873 DOI: 10.1016/j.tibs.2021.12.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2021] [Revised: 12/07/2021] [Accepted: 12/09/2021] [Indexed: 12/26/2022]
Abstract
The sterol-sensing domain (SSD) is present in several membrane proteins that function in cholesterol metabolism, transport, and signaling. Recent progress in structural studies of SSD-containing proteins, such as sterol regulatory element-binding protein (SREBP)-cleavage activating protein (Scap), Patched, Niemann-Pick disease type C1 (NPC1), and related proteins, reveals a conserved core that is essential for their sterol-dependent functions. This domain, by its name, 'senses' the presence of sterol substrates through interactions and may modulate protein behaviors with changing sterol levels. We summarize recent advances in structural and mechanistic investigations of these proteins and propose to divide them to two classes: M for 'moderator' proteins that regulate sterol metabolism in response to membrane sterol levels, and T for 'transporter' proteins that harbor inner tunnels for cargo trafficking across cellular membranes.
Collapse
Affiliation(s)
- Xuelan Wu
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - Renhong Yan
- Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, 18 Shilongshan Road, Hangzhou 310024, Zhejiang Province, China; Institute of Biology, Westlake Institute for Advanced Study, 18 Shilongshan Road, Hangzhou 310024, Zhejiang Province, China
| | - Pingping Cao
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Hongwu Qian
- Ministry of Education (MOE) Key Laboratory of Membraneless Organelles and Cellular Dynamics, Hefei National Laboratory for Physical Sciences at the Microscale, and Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China.
| | - Nieng Yan
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
| |
Collapse
|
19
|
Steck TL, Tabei SMA, Lange Y. A basic model for cell cholesterol homeostasis. Traffic 2021; 22:471-481. [PMID: 34528339 DOI: 10.1111/tra.12816] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 08/26/2021] [Accepted: 09/13/2021] [Indexed: 11/30/2022]
Abstract
Cells manage their cholesterol by negative feedback using a battery of sterol-responsive proteins. How these activities are coordinated so as to specify the abundance and distribution of the sterol is unclear. We present a simple mathematical model that addresses this question. It assumes that almost all of the cholesterol is associated with phospholipids in stoichiometric complexes. A small fraction of the sterol is uncomplexed and thermodynamically active. It equilibrates among the organelles, setting their sterol level according to the affinity of their phospholipids. The activity of the homeostatic proteins in the cytoplasmic membranes is then set by their fractional saturation with uncomplexed cholesterol in competition with the phospholipids. The high-affinity phospholipids in the plasma membrane (PM) are filled to near stoichiometric equivalence, giving it most of the cell sterol. Notably, the affinity of the phospholipids in the endomembranes (EMs) is lower by orders of magnitude than that of the phospholipids in the PM. Thus, the small amount of sterol in the EMs rests far below stoichiometric capacity. Simulations match a variety of experimental data. The model captures the essence of cell cholesterol homeostasis, makes coherent a diverse set of experimental findings, provides a surprising prediction and suggests new experiments.
Collapse
Affiliation(s)
- Theodore L Steck
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
| | - S M Ali Tabei
- Department of Physics, University of Northern Iowa, Cedar Falls, Iowa, USA
| | - Yvonne Lange
- Department of Pathology, Rush University Medical Center, Chicago, Illinois, USA
| |
Collapse
|
20
|
Bian X, Liu R, Meng Y, Xing D, Xu D, Lu Z. Lipid metabolism and cancer. J Exp Med 2021; 218:211616. [PMID: 33601415 PMCID: PMC7754673 DOI: 10.1084/jem.20201606] [Citation(s) in RCA: 359] [Impact Index Per Article: 119.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 10/15/2020] [Accepted: 10/26/2020] [Indexed: 02/05/2023] Open
Abstract
Dysregulation in lipid metabolism is among the most prominent metabolic alterations in cancer. Cancer cells harness lipid metabolism to obtain energy, components for biological membranes, and signaling molecules needed for proliferation, survival, invasion, metastasis, and response to the tumor microenvironment impact and cancer therapy. Here, we summarize and discuss current knowledge about the advances made in understanding the regulation of lipid metabolism in cancer cells and introduce different approaches that have been clinically used to disrupt lipid metabolism in cancer therapy.
Collapse
Affiliation(s)
- Xueli Bian
- Cancer Institute of The Affiliated Hospital of Qingdao University and Qingdao Cancer Institute, Qingdao, China
| | - Rui Liu
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, Chinese Academy of Medical Sciences Research Unit of Oral Carcinogenesis and Management, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Ying Meng
- Zhejiang Provincial Key Laboratory of Pancreatic Disease, The First Affiliated Hospital, and Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou, China
| | - Dongming Xing
- Cancer Institute of The Affiliated Hospital of Qingdao University and Qingdao Cancer Institute, Qingdao, China.,School of Life Sciences, Tsinghua University, Beijing, China
| | - Daqian Xu
- Zhejiang Provincial Key Laboratory of Pancreatic Disease, The First Affiliated Hospital, and Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou, China
| | - Zhimin Lu
- Zhejiang Provincial Key Laboratory of Pancreatic Disease, The First Affiliated Hospital, and Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou, China.,Zhejiang University Cancer Center, Hangzhou, China
| |
Collapse
|
21
|
Zhu T, Zhao J, Zhuo S, Hu Z, Ouyang S, Wunier, Yu S, Chen Y, Li Y, Le Y. High Fat Diet and High Cholesterol Diet Reduce Hepatic Vitamin D-25-Hydroxylase Expression and Serum 25-Hydroxyvitamin D 3 Level through Elevating Circulating Cholesterol, Glucose, and Insulin Levels. Mol Nutr Food Res 2021; 65:e2100220. [PMID: 34448353 DOI: 10.1002/mnfr.202100220] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 08/04/2021] [Indexed: 12/20/2022]
Abstract
SCOPE Low circulating 25-hydroxyvitamin D (25(OH)D) levels associate with obesity, diabetes, and hyperlipidemia, but the underlying mechanisms remain uncertain. As energy-dense diet contributes to these disorders, this study investigates whether diet could impair vitamin D metabolism. METHODS AND RESULTS Compared with control chow-fed mice, high fat diet (HFD)-fed mice show lower serum 25(OH)D3 and 1,25(OH)2 D3 levels, lower hepatic vitamin D 25-hydroxylase Cyp2r1 expression but comparable renal vitamin D metabolic enzymes expression. Time course studies show that after HFD feeding, the serum concentrations of cholesterol, triglycerides, fatty acids, glucose, and insulin elevate sequentially and before the reduction of hepatic Cyp2r1 expression and serum 25(OH)D3 levels. Hepatic Cyp2r1 expression also reduces after consuming high fat and high sucrose diet. After high cholesterol diet feeding, serum total cholesterol rises and hepatic Cyp2r1 expression decreases ahead of the reduction of serum 25(OH)D3 . In vitro studies demonstrate that high concentrations of cholesterol, glucose, and insulin significantly inhibit Cyp2r1expression in primary murine hepatocytes. Further studies show that dietary restriction in HFD-fed mice ameliorates hypercholesterolemia, hyperglycemia, and hypertriglyceridemia, and elevates hepatic Cyp2r1 expression and serum 25(OH)D3 level. CONCLUSION These findings suggest that diet-induced elevation of circulating cholesterol, glucose, and insulin reduces serum 25(OH)D3 level through suppressing hepatic Cyp2r1 expression.
Collapse
Affiliation(s)
- Tengfei Zhu
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, 200031, China.,School of Public Health, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Jingyu Zhao
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, 200031, China
| | - Shu Zhuo
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, 200031, China
| | - Zhimin Hu
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, 200031, China
| | - Shuyu Ouyang
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, 200031, China
| | - Wunier
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, 200031, China
| | - Shuting Yu
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, 200031, China
| | - Yan Chen
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, 200031, China
| | - Yu Li
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, 200031, China
| | - Yingying Le
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, 200031, China.,Key Laboratory of Food Safety Risk Assessment, Ministry of Health, Beijing, 100021, China
| |
Collapse
|
22
|
Sharpe LJ, Coates HW, Brown AJ. Post-translational control of the long and winding road to cholesterol. J Biol Chem 2021; 295:17549-17559. [PMID: 33453997 DOI: 10.1074/jbc.rev120.010723] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 10/12/2020] [Indexed: 01/19/2023] Open
Abstract
The synthesis of cholesterol requires more than 20 enzymes, many of which are intricately regulated. Post-translational control of these enzymes provides a rapid means for modifying flux through the pathway. So far, several enzymes have been shown to be rapidly degraded through the ubiquitin-proteasome pathway in response to cholesterol and other sterol intermediates. Additionally, several enzymes have their activity altered through phosphorylation mechanisms. Most work has focused on the two rate-limiting enzymes: 3-hydroxy-3-methylglutaryl CoA reductase and squalene monooxygenase. Here, we review current literature in the area to define some common themes in the regulation of the entire cholesterol synthesis pathway. We highlight the rich variety of inputs controlling each enzyme, discuss the interplay that exists between regulatory mechanisms, and summarize findings that reveal an intricately coordinated network of regulation along the cholesterol synthesis pathway. We provide a roadmap for future research into the post-translational control of cholesterol synthesis, and no doubt the road ahead will reveal further twists and turns for this fascinating pathway crucial for human health and disease.
Collapse
Affiliation(s)
- Laura J Sharpe
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Hudson W Coates
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia.
| |
Collapse
|
23
|
The Degron Architecture of Squalene Monooxygenase and How Specific Lipids Calibrate Levels of This Key Cholesterol Synthesis Enzyme. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021. [PMID: 32979157 DOI: 10.1007/5584_2020_583] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register]
Abstract
Cholesterol synthesis is a fundamental process that contributes to cellular cholesterol homeostasis. Cells execute transcriptional and post-translational mechanisms to control the abundance of enzymes of the cholesterol synthesis pathway, consequently affecting cholesterol production. One such highly tuned enzyme is squalene monooxygenase (SM), which catalyzes a rate-limiting step in the pathway. A well-characterized mechanism is the cholesterol-mediated degradation of SM. Notably, lipids (cholesterol, plasmalogens, squalene, and unsaturated fatty acids) can act as cellular signals that either promote or reduce SM degradation. The N-terminal region of SM consists of the shortest known cholesterol-responsive degron, characterized by atypical membrane anchoring structures, namely a re-entrant loop and an amphipathic helix. SM also undergoes non-canonical ubiquitination on serine, a relatively uncommon attachment site for ubiquitination. The structure of the catalytic domain of SM has been solved, providing insights into the catalytic mechanisms and modes of inhibition by well-known SM inhibitors, some of which have been effective in lowering cholesterol levels in animal models. Certain human cancers have been linked to dysregulation of SM levels and activity, further emphasizing the relevance of SM in health and disease.
Collapse
|
24
|
Kang JA, Jeon YJ. How Is the Fidelity of Proteins Ensured in Terms of Both Quality and Quantity at the Endoplasmic Reticulum? Mechanistic Insights into E3 Ubiquitin Ligases. Int J Mol Sci 2021; 22:ijms22042078. [PMID: 33669844 PMCID: PMC7923238 DOI: 10.3390/ijms22042078] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 02/16/2021] [Accepted: 02/16/2021] [Indexed: 02/06/2023] Open
Abstract
The endoplasmic reticulum (ER) is an interconnected organelle that plays fundamental roles in the biosynthesis, folding, stabilization, maturation, and trafficking of secretory and transmembrane proteins. It is the largest organelle and critically modulates nearly all aspects of life. Therefore, in the endoplasmic reticulum, an enormous investment of resources, including chaperones and protein folding facilitators, is dedicated to adequate protein maturation and delivery to final destinations. Unfortunately, the folding and assembly of proteins can be quite error-prone, which leads to the generation of misfolded proteins. Notably, protein homeostasis, referred to as proteostasis, is constantly exposed to danger by flows of misfolded proteins and subsequent protein aggregates. To maintain proteostasis, the ER triages and eliminates terminally misfolded proteins by delivering substrates to the ubiquitin–proteasome system (UPS) or to the lysosome, which is termed ER-associated degradation (ERAD) or ER-phagy, respectively. ERAD not only eliminates misfolded or unassembled proteins via protein quality control but also fine-tunes correctly folded proteins via protein quantity control. Intriguingly, the diversity and distinctive nature of E3 ubiquitin ligases determine efficiency, complexity, and specificity of ubiquitination during ERAD. ER-phagy utilizes the core autophagy machinery and eliminates ERAD-resistant misfolded proteins. Here, we conceptually outline not only ubiquitination machinery but also catalytic mechanisms of E3 ubiquitin ligases. Further, we discuss the mechanistic insights into E3 ubiquitin ligases involved in the two guardian pathways in the ER, ERAD and ER-phagy. Finally, we provide the molecular mechanisms by which ERAD and ER-phagy conduct not only protein quality control but also protein quantity control to ensure proteostasis and subsequent organismal homeostasis.
Collapse
Affiliation(s)
- Ji An Kang
- Department of Biochemistry, College of Medicine, Chungnam National University, Daejeon 35015, Korea;
- Department of Medical Science, College of Medicine, Chungnam National University, Daejeon 35015, Korea
| | - Young Joo Jeon
- Department of Biochemistry, College of Medicine, Chungnam National University, Daejeon 35015, Korea;
- Department of Medical Science, College of Medicine, Chungnam National University, Daejeon 35015, Korea
- Correspondence:
| |
Collapse
|
25
|
Ishihara T, Kanon H, Ban-Ishihara R, Ishihara N. Multiple assay systems to analyze the dynamics of mitochondrial nucleoids in living mammalian cells. Biochim Biophys Acta Gen Subj 2021; 1865:129874. [PMID: 33607223 DOI: 10.1016/j.bbagen.2021.129874] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2020] [Revised: 01/18/2021] [Accepted: 02/09/2021] [Indexed: 10/22/2022]
Abstract
BACKGROUND Mitochondria, which play a critical role in energy production by oxidative respiration, are highly dynamic organelles and their double membranes undergo frequent events of fusion and fission. Mitochondria are believed to be derived from the endosymbiosis of proteobacteria, and thus mitochondria still contain their own DNA, mitochondrial DNA (mtDNA). Several copies of mtDNA form mitochondrial nucleoid with DNA-binding proteins. Recently, the morphology and distribution of the mitochondrial membrane and nucleoid were reported to be cooperatively regulated during their dynamic movement. However, the molecular mechanism is unclear, because the involved molecules are poorly understood, and suitable techniques to analyze nucleoid have not been fully developed. RESULTS To solve these issues, we examined the molecular mechanism of nucleoid dynamics by two approaches. First, we constructed a new probe to perform live imaging of nucleoid dynamics using the DNA-binding domain of mitochondrial transcriptional factor A (TFAM) and the photo-convertible fluorescent protein Kikume Green-Red (KikGR). Nucleoids were visualized stably for a long period using the new probe. Second, we searched for nucleoid regulatory factors by small interfering RNA screening using HeLa cells and identified a subset of MARCH family ubiquitin ligases that affect nucleoid morphology. CONCLUSION The factors and probe, reported in this study, would be useful to reveal novel mechanisms of mitochondrial regulation. GENERAL SIGNIFICANCE The mtDNA dynamics should be concerned in the regulation of mitochondrial activity and its quality control, associated with mitochondrial membrane dynamics.
Collapse
Affiliation(s)
- Takaya Ishihara
- Department of Biological Sciences, Graduate School of Science, Osaka University, Japan; Department of Protein Biochemistry, Institute of Life Science, Kurume University, Japan.
| | - Hirotaka Kanon
- Department of Biological Sciences, Graduate School of Science, Osaka University, Japan
| | - Reiko Ban-Ishihara
- Department of Protein Biochemistry, Institute of Life Science, Kurume University, Japan
| | - Naotada Ishihara
- Department of Biological Sciences, Graduate School of Science, Osaka University, Japan; Department of Protein Biochemistry, Institute of Life Science, Kurume University, Japan.
| |
Collapse
|
26
|
Ninagawa S, George G, Mori K. Mechanisms of productive folding and endoplasmic reticulum-associated degradation of glycoproteins and non-glycoproteins. Biochim Biophys Acta Gen Subj 2020; 1865:129812. [PMID: 33316349 DOI: 10.1016/j.bbagen.2020.129812] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2020] [Revised: 12/09/2020] [Accepted: 12/09/2020] [Indexed: 12/22/2022]
Abstract
BACKGROUND The quality of proteins destined for the secretory pathway is ensured by two distinct mechanisms in the endoplasmic reticulum (ER): productive folding of newly synthesized proteins, which is assisted by ER-localized molecular chaperones and in most cases also by disulfide bond formation and transfer of an oligosaccharide unit; and ER-associated degradation (ERAD), in which proteins unfolded or misfolded in the ER are recognized and processed for delivery to the ER membrane complex, retrotranslocated through the complex with simultaneous ubiquitination, extracted by AAA-ATPase to the cytosol, and finally degraded by the proteasome. SCOPE OF REVIEW We describe the mechanisms of productive folding and ERAD, with particular attention to glycoproteins versus non-glycoproteins, and to yeast versus mammalian systems. MAJOR CONCLUSION Molecular mechanisms of the productive folding of glycoproteins and non-glycoproteins mediated by molecular chaperones and protein disulfide isomerases are well conserved from yeast to mammals. Additionally, mammals have gained an oligosaccharide structure-dependent folding cycle for glycoproteins. The molecular mechanisms of ERAD are also well conserved from yeast to mammals, but redundant expression of yeast orthologues in mammals has been encountered, particularly for components involved in recognition and processing of glycoproteins and components of the ER membrane complex involved in retrotranslocation and simultaneous ubiquitination of glycoproteins and non-glycoproteins. This may reflect an evolutionary consequence of increasing quantity or quality needs toward mammals. GENERAL SIGNIFICANCE The introduction of innovative genome editing technology into analysis of the mechanisms of mammalian ERAD, as exemplified here, will provide new insights into the pathogenesis of various diseases.
Collapse
Affiliation(s)
- Satoshi Ninagawa
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
| | - Ginto George
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Kazutoshi Mori
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
| |
Collapse
|
27
|
Scott NA, Sharpe LJ, Brown AJ. The E3 ubiquitin ligase MARCHF6 as a metabolic integrator in cholesterol synthesis and beyond. Biochim Biophys Acta Mol Cell Biol Lipids 2020; 1866:158837. [PMID: 33049405 DOI: 10.1016/j.bbalip.2020.158837] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 09/29/2020] [Accepted: 10/02/2020] [Indexed: 12/19/2022]
Abstract
MARCHF6 is a large multi-pass E3 ubiquitin ligase embedded in the membranes of the endoplasmic reticulum. It participates in endoplasmic reticulum associated degradation, including autoubiquitination, and many of its identified substrates are involved in sterol and lipid metabolism. Post-translationally, MARCHF6 expression is attuned to cholesterol status, with high cholesterol preventing its degradation and hence boosting MARCHF6 levels. By modulating MARCHF6 activity, cholesterol may regulate other aspects of cell metabolism beyond the known repertoire. Whilst we have learnt much about MARCHF6 in the past decade, there are still many more mysteries to be unravelled to fully understand its regulation, substrates, and role in human health and disease.
Collapse
Affiliation(s)
- Nicola A Scott
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Laura J Sharpe
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia.
| |
Collapse
|
28
|
Lange Y, Steck TL. Active cholesterol 20 years on. Traffic 2020; 21:662-674. [PMID: 32930466 DOI: 10.1111/tra.12762] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 09/08/2020] [Accepted: 09/10/2020] [Indexed: 12/13/2022]
Abstract
This review considers the following hypotheses, some well-supported and some speculative. Almost all of the sterol molecules in plasma membranes are associated with bilayer phospholipids in complexes of varied strength and stoichiometry. These complexes underlie many of the material properties of the bilayer. The small fraction of cholesterol molecules exceeding the binding capacity of the phospholipids is thermodynamically active and serves diverse functions. It circulates briskly among the cell membranes, particularly through contact sites linking the organelles. Active cholesterol provides the upstream feedback signal to multiple mechanisms governing plasma membrane homeostasis, pegging the sterol level to a threshold set by its phospholipids. Active cholesterol could also be the cargo for various inter-organelle transporters and the form excreted from cells by reverse transport. Furthermore, it is integral to the function of caveolae; a mediator of Hedgehog regulation; and a ligand for the binding of cytolytic toxins to membranes. Active cholesterol modulates a variety of plasma membrane proteins-receptors, channels and transporters-at least in vitro.
Collapse
Affiliation(s)
- Yvonne Lange
- Department of Pathology, Rush University Medical Center, Chicago, Illinois, USA
| | - Theodore L Steck
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
| |
Collapse
|
29
|
The cholesterol synthesis enzyme lanosterol 14α-demethylase is post-translationally regulated by the E3 ubiquitin ligase MARCH6. Biochem J 2020; 477:541-555. [PMID: 31904814 PMCID: PMC6993871 DOI: 10.1042/bcj20190647] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 12/22/2019] [Accepted: 01/02/2020] [Indexed: 01/07/2023]
Abstract
Cholesterol synthesis is a tightly controlled pathway, with over 20 enzymes involved. Each of these enzymes can be distinctly regulated, helping to fine-tune the production of cholesterol and its functional intermediates. Several enzymes are degraded in response to increased sterol levels, whilst others remain stable. We hypothesised that an enzyme at a key branch point in the pathway, lanosterol 14α-demethylase (LDM) may be post-translationally regulated. Here, we show that the preceding enzyme, lanosterol synthase is stable, whilst LDM is rapidly degraded. Surprisingly, this degradation is not triggered by sterols. However, the E3 ubiquitin ligase membrane-associated ring-CH-type finger 6 (MARCH6), known to control earlier rate-limiting steps in cholesterol synthesis, also control levels of LDM and the terminal cholesterol synthesis enzyme, 24-dehydrocholesterol reductase. Our work highlights MARCH6 as the first example of an E3 ubiquitin ligase that targets multiple steps in a biochemical pathway and indicates new facets in the control of cholesterol synthesis.
Collapse
|
30
|
van den Boomen DJH, Volkmar N, Lehner PJ. Ubiquitin-mediated regulation of sterol homeostasis. Curr Opin Cell Biol 2020; 65:103-111. [PMID: 32580085 DOI: 10.1016/j.ceb.2020.04.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2020] [Revised: 04/03/2020] [Accepted: 04/26/2020] [Indexed: 11/19/2022]
Abstract
Cholesterol is an essential component of mammalian membranes, and its homeostasis is strictly regulated, with imbalances causing atherosclerosis, Niemann Pick disease, and familial hypercholesterolemia. Cellular cholesterol supply is mediated by LDL-cholesterol import and de novo cholesterol biosynthesis, and both pathways are adjusted to cellular demand by the cholesterol-sensitive SREBP2 transcription factor. Cholesterol homeostasis is modulated by a wide variety of metabolic pathways and the ubiquitination machinery, in particular E3 ubiquitin ligases. In this article, we review recent progress in understanding the role of E3 ubiquitin ligases in the metabolic control of cellular sterol homeostasis.
Collapse
Affiliation(s)
- Dick J H van den Boomen
- Cambridge Institute of Therapeutic Immunology & Infectious Disease, University of Cambridge, Cambridge, United Kingdom
| | - Norbert Volkmar
- Cambridge Institute of Therapeutic Immunology & Infectious Disease, University of Cambridge, Cambridge, United Kingdom
| | - Paul J Lehner
- Cambridge Institute of Therapeutic Immunology & Infectious Disease, University of Cambridge, Cambridge, United Kingdom.
| |
Collapse
|
31
|
Capell-Hattam IM, Sharpe LJ, Qian L, Hart-Smith G, Prabhu AV, Brown AJ. Twin enzymes, divergent control: The cholesterogenic enzymes DHCR14 and LBR are differentially regulated transcriptionally and post-translationally. J Biol Chem 2020; 295:2850-2865. [PMID: 31911440 PMCID: PMC7049974 DOI: 10.1074/jbc.ra119.011323] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 12/13/2019] [Indexed: 01/07/2023] Open
Abstract
Cholesterol synthesis is a tightly regulated process, both transcriptionally and post-translationally. Transcriptional control of cholesterol synthesis is relatively well-understood. However, of the ∼20 enzymes in cholesterol biosynthesis, post-translational regulation has only been examined for a small number. Three of the four sterol reductases in cholesterol production, 7-dehydrocholesterol reductase (DHCR7), 14-dehydrocholesterol reductase (DHCR14), and lamin-B receptor (LBR), share evolutionary ties with a high level of sequence homology and predicted structural homology. DHCR14 and LBR uniquely share the same Δ-14 reductase activity in cholesterol biosynthesis, yet little is known about their post-translational regulation. We have previously identified specific modes of post-translational control of DHCR7, but it is unknown whether these regulatory mechanisms are shared by DHCR14 and LBR. Using CHO-7 cells stably expressing epitope-tagged DHCR14 or LBR, we investigated the post-translational regulation of these enzymes. We found that DHCR14 and LBR undergo differential post-translational regulation, with DHCR14 being rapidly turned over, triggered by cholesterol and other sterol intermediates, whereas LBR remained stable. DHCR14 is degraded via the ubiquitin-proteasome system, and we identified several DHCR14 and DHCR7 putative interaction partners, including a number of E3 ligases that modulate DHCR14 levels. Interestingly, we found that gene expression across an array of human tissues showed a negative relationship between the C14-sterol reductases; one enzyme or the other tends to be predominantly expressed in each tissue. Overall, our findings indicate that whereas LBR tends to be the constitutively active C14-sterol reductase, DHCR14 levels are tunable, responding to the local cellular demands for cholesterol.
Collapse
Affiliation(s)
- Isabelle M Capell-Hattam
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Laura J Sharpe
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Lydia Qian
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Gene Hart-Smith
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia; Department of Molecular Sciences, Macquarie University, Macquarie Park, New South Wales 2109, Australia
| | - Anika V Prabhu
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia.
| |
Collapse
|
32
|
Mechanisms and regulation of cholesterol homeostasis. Nat Rev Mol Cell Biol 2019; 21:225-245. [DOI: 10.1038/s41580-019-0190-7] [Citation(s) in RCA: 450] [Impact Index Per Article: 90.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/24/2019] [Indexed: 12/14/2022]
|
33
|
Coates HW, Chua NK, Brown AJ. Consulting prostate cancer cohort data uncovers transcriptional control: Regulation of the MARCH6 gene. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1864:1656-1668. [PMID: 31422115 DOI: 10.1016/j.bbalip.2019.08.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 08/01/2019] [Accepted: 08/14/2019] [Indexed: 12/28/2022]
Abstract
Cholesterol accumulation is a hallmark of prostate cancer (PCa) enabled by the upregulation of its synthesis, which presents a potential therapeutic target. This pathway is suppressed by the E3 ubiquitin ligase membrane-associated RING-CH-type finger 6 (MARCH6); however, little is known of MARCH6 regulation, particularly at the transcriptional level. Here, we consulted large transcriptomic PCa datasets to investigate transcription factors and DNA sequence elements that regulate the MARCH6 gene. Amongst 498 primary PCa tissues of The Cancer Genome Atlas, we identified a striking positive correlation between MARCH6 and androgen receptor (AR) gene expression (r = 0.81, p < 1 × 10-117) that held in other primary tumour datasets. Two putative androgen response elements were identified in the MARCH6 gene using motif prediction and mining of publicly accessible chromatin immunoprecipitation-sequencing data. However, MARCH6 expression was not androgen-responsive in luciferase reporter and qRT-PCR assays. Instead, we established that the MARCH6-AR correlation in primary PCa is due to common regulation by the transcription factor Sp1. We located a region 100 bp downstream of the MARCH6 transcriptional start site that contains three Sp1 binding sites and strongly upregulates promoter activity. The functionality of this region, and Sp1-mediated upregulation of MARCH6, was confirmed using pharmacological and genetic inhibition of Sp1. Moreover, modulation of Sp1 activity affected the stability of squalene monooxygenase, a cholesterol biosynthesis enzyme and MARCH6 substrate. We thus establish Sp1 as the first known regulator of the MARCH6 gene and demonstrate that interrogation of transcriptomic datasets can assist in the de novo inference of transcriptional regulation.
Collapse
Affiliation(s)
- Hudson W Coates
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, Australia
| | - Ngee Kiat Chua
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, Australia
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, Australia.
| |
Collapse
|
34
|
Valosin-containing protein mediates the ERAD of squalene monooxygenase and its cholesterol-responsive degron. Biochem J 2019; 476:2545-2560. [DOI: 10.1042/bcj20190418] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 08/27/2019] [Accepted: 08/29/2019] [Indexed: 12/17/2022]
Abstract
AbstractSqualene monooxygenase (SM) is an essential rate-limiting enzyme in cholesterol synthesis. SM degradation is accelerated by excess cholesterol, and this requires the first 100 amino acids of SM (SM N100). This process is part of a protein quality control pathway called endoplasmic reticulum-associated degradation (ERAD). In ERAD, SM is ubiquitinated by MARCH6, an E3 ubiquitin ligase located in the endoplasmic reticulum (ER). However, several details of the ERAD process for SM remain elusive, such as the extraction mechanism from the ER membrane. Here, we used SM N100 fused to GFP (SM N100-GFP) as a model degron to investigate the extraction process of SM in ERAD. We showed that valosin-containing protein (VCP) is important for the cholesterol-accelerated degradation of SM N100-GFP and SM. In addition, we revealed that VCP acts following ubiquitination of SM N100-GFP by MARCH6. We demonstrated that the amphipathic helix (Gln62–Leu73) of SM N100-GFP is critical for regulation by VCP and MARCH6. Replacing this amphipathic helix with hydrophobic re-entrant loops promoted degradation in a VCP-dependent manner. Finally, we showed that inhibiting VCP increases cellular squalene and cholesterol levels, indicating a functional consequence for VCP in regulating the cholesterol synthesis pathway. Collectively, we established VCP plays a key role in ERAD that contributes to the cholesterol-mediated regulation of SM.
Collapse
|